Thermostatic control for electric switches



Aug. 7, 1928. 1,679,649

J. R- COOK THERMOTATIC CONTROL FOR ELECTRIC SWITCHES Filed July 5, 1924amoentoz pam m gmtw' Patented Aug. 7, 1928.

UNITED STATES PATENT OFFICE.

JOEL B. COOK, OI CLEVELAND, OHIO, ASSIGNOR, BY HESNE A SSIGNMENTS, TOWEST- INGHOUSE ELECTRIC & HANUFACTURIN G COMPANY, A CORPORATION OF PENN-BYLVANIA.

THERMOSTA'IIC CONTROL Application filed July 3,

This invention is concerned with the control of electric switches andhas for its object the provision of a simple, compact and efiicientthermostatic control in an electric circuit breaker.

A more specific object of my invention is the provision of an electriccurrent-carrying bimetallic thermostatic element to comprise amechanical control for an electrical switch and to constitute,permanently, a part of the circuit controlled b the switch.

Other objects my invention will be hereinafter set forth in thefollowing description referring to the accompanying drawingsillustrating a preferred embodiment thereof. The essentialcharacteristics are summarized in the claims.

In the drawings Fig. 1 is a plan View of a simple switch mechanismincorporating my thermostatic control; Fig. 2 is an enlarged sideelevation of a thermostatic element; and Fig. 3 is a cross-sectionalview taken through the base of the switch along the line 3-3 of 1 andillustrating. a convenient mounting for the thermostatic element.

My invention, as shown in the drawings, may-.be embodied in a switch orcircuit breaker in a very simple manner to normally maintain thecontacts of the switch closed by opposing the action of a switchopeninmeans, usually a spring. In Fig. 1, a switc or circuit breaker is shownof the general type disclosed and claimed in my prior applicationpertaining to an electric switch filed Sept. 18, 1922, Ser. No. 588,755For convenience in illustration, the switch may comprise a base 6 formedof suitable insulating material and upon which are mounted stationarycontacts 7 and 8 which may comprise L-shaped members having outwardlyextending contacting portions 9 and 10, respectively. The contactingsurfaces thereof may be radially disposed whereby movable contactmembers 11 and 12 may be mounted to swing about a pivotal center 13. Themovable members 11 and '12:

may be mounted upon the free ends of a resilient bridging member 14insulatingly secured at its center to a revoluble bridge-sup:

porting member16. The free arms 14 and 14" of the bridging member maythus comprise a resilient supporting means for the r013. ELECTRICswrrcnns.

1924. Serial No. 723,888.

movable contacts 11 and 12, respectively, to permit proper contactbetween the currentconductmg members 9, 11, and 12, respectively.

The supporting member 16 may be mounted upon a staff 18 pivotallysupported by the base 6, the shaft being actuated in a well known mannerby a handle or knob, not shown. To resiliently bias the member 16"spring member 20 may surround a hub portion 16 of the bridge-supportingmember 16 with one end secured to the staif and the other end inengagement with an outwardly extendinglug on the supporting member 16.The spring 20 may be tensioned by the manual turning of the stafi' 18 tobring the contacts 11 and 12 into closing relationship with thestationar contacts 9 and 10 respectively. The mem er 16 may bemaintained in such position by. the action of a deflectable currentcarrying bi metallic thermostatic member 25, which may be mounted tocomprise a cantilever with the free end 26 thereof serving to engage aprojecting member 27 insulatingly mounted upon the projecting lug 22 ofthe member 16.

The thermostatic member 25, as shown in Fig. 2, may be formed of abi-metallicsheet to comprise a loop of U-shape, as shown, with the ends27 and 28 of the ends of the loop secured to supporting members 30 and31, respectively. The latter members may be of an L-shape, as shown inFig. 3, with a suitable insulating member 34 disposed therebetween,whereby the looped thermostatic member may comprise a permanent part ofthe circuit controlled by the separable contacts. The mounting of thethermostatic member, as shown in Fig. 3, is accordingly such that leadwire 35 may be connected to a terminal-securing bolt 42 which serves toclamp the supporting members of the thermostatic element to theinsulating base 6 with a nut 38 serving as a tightening or clampingmedium. The current would thus come'into the switch through the line 35through the securing bolt 42, through the member 31, traverse the lower.leg of the thermostatic element 25, as indicated by the arrow in Figs. 2and 3, and return along the upper leg. The current would then pass to.the connected terminal support 30 and thence through the bolt 36 and toa line 39 connected to a securing bolt 41, which clamps the'stationarcontact member 8 to the base, and therea terthrough the bridge member 14to the stationary contact 7 and then out through the line 40 connectedto a securing bolt 44.

The thermostat 25 may be formed from a bimetal sheet in a well knownmanner whereby the inner side may have a greater coefiicient ofexpansion than the outer side to cause the thermostat to curl or deflectoutwardly. Hence, when an overload condition exists in the line 35 and40, the resistance of the bi-me-tal comprising the thermostatic elementwill cause the formation of sufficient heat in the element to effect itsoutward deflection to release the detent member 27 and permit the springmember 20 to swing the contact-supporting member 16 to open position,whereupon the thermostatic element 25 will immediately cool and assume.its normal position and, upon resetting of the contact supporting member16, the member 27 will wipe over the inner face of the element,springing it outwardly until the end thereof is. passed by the detentmember 27, whereupon it will spring inwardly and retain the element ofthe switch, as shown in Fig. 1, until 'another over-load conditionoccurs in the line.

It will be seen that the shape of the thermostatic element is such thatcurrent travber whereby thegthermostatic member will erses the lengththereof in two directions and that there is no electrical connectionbetween the element and movable parts of the switch where undue arcingor sparking might occur. The element remains connected in the circuitregardless of whether the switch is open or closed andis of such simpleform that the resistance and corresponding deflecting characteristicsmay be accurately predetermined, permitting the element to bemanufactured in large quantities without necessitating the calibrationof each element to determine its resistance and defleetivecharacteristics.

I cla1m- 1. In an electric switch the combination of a bimetalliccurrent carrying thermostatic member and a mounting therefor, saidmember being substantially U-shaped and the mounting comprising a basemember and 'a pair of superposed current carrying members electricallyinsulated from each other and disposed at one side of the vU but inplanes parallel therewith, one member being connected to'and supportingone leg and the other the other leg of the thermostatic memextend alongthe base.

2. In an electric switch the combination of stationary. contact members,swingable ontact members adaptedto bridge the staabutment substantiallyat right angles with relation to the abutting surface thereof to opposethe swinging movement of the supporting means.

3. In an electric switch, the combination of a bimetalliccurrent-carrying thermostatic member and a mounting therefor, saidmember being loop shaped and the mounting comprising a base member andtwo currentcarrying members each being connected to a respective end ofthe loop member and being in superposed relation in planes parallel tothe general plane of the loop whereby the thermostatic member may besuspended in ofiset substan ially parallel relation to the ase.

4. In an electric switch, the combination of a bimetalliccurrent-carrying thermostatic member mounted to comprise a cantilever.said member being substantially U-shaped and the mounting comprising apair of L shaped current-carrying members electrically insulated fromeach other and in superposed relation, each member supporting a leg ofthe thermostatic member in offset but substantially parallel relation tothe base.

5. In combination, a thermostatic element forming part of the circuit ofan electric switch comprising a looped bimetallic member having legsseparated and lying in vertical alignment with reference to a commonbase, a pair of metallic supporting members individually secured to saidle s at their ends and in. overlying relation but insulated from eachother, and means passing through such supporting members and adapted toserve as an electric conductor lead for one-of them and to clamp bothsaid members to such base.

6. In an electric switch, the combination of a base, a looped bimetallicmember conneetedto permanently comprise a part of the switch circuit,means to 'hold the member with the legs of the loop in verticalalignment with reference to the base and serving to establishconnections to the switch circuit whereby the bimetallic member isconsignature.

; JOEL R. COOK.

